Gzip decompress

Your file with the .gz stripped off, so archive.tar.gz comes back as archive.tar. If the name does not end in a recognised suffix, .out is appended instead, so the result never overwrites the name it came from. The bytes are exactly what was compressed, since gzip is lossless.

Run Extract tar on it. A .tar.gz is a tar archive that was then gzipped, so decompressing gives you the plain tar and the second step unpacks the files. That reader handles plain USTAR archives with regular files and nested paths.

No declared size guard, unlike Extract ZIP. A gzip stream does not announce its uncompressed size up front the way a zip entry does, so the data is inflated into memory as it comes. A deliberately crafted bomb, or an ordinary large archive, can therefore exhaust the tab. Use a desktop tool that streams to disk for anything huge.

Because the bytes are not a valid gzip stream. That covers a truncated download, a file renamed to .gz that is a zip or a plain tar, and a corrupted archive. Check the real type with Detect file type if you are not sure what you have.

No. This reads the gzip format only. Use Extract ZIP for a zip, Zlib decompress for a zlib stream and Deflate decompress for a raw deflate stream. Bzip2 and xz are not supported by any tool here. If you are not sure what you have, run Detect file type first, since it reads the magic bytes instead of trusting the extension.

No. The file is decompressed in a Web Worker in your own tab, with the compressed input and the full expanded output both held in memory. Nothing is sent to a server, and the page works offline after your first visit.